When used in this specification "dye" means coloring matter in liquid form and "pigment" means coloring matter in particulate form.
Conventional dyes used in fabric printer ribbons are not well suited for printing bar code for infrared sensing. A ribbon can be initially loaded at the factory with sufficient dye so that bar code printed can be sensed conventionally, the dye being, for example, conventional nigrosine dye. Replenishment of such high loading of dye by re-inking in a cartridge has not been possible, and this is complicated by the fact that conventional dye-based inks tend to become much more viscous over time.
Dye, rather than pigment, in such inks provides advantages in the feeding of the ribbon. Ribbon with dye feeds more easily than ribbons with pigments. Such ribbons typically are packed or stuffed together in folds in a chamber of a cartridge. Dye permits the back pressure of the ribbon to be higher for the same resistance to feeding. Pigments add to the overall stiffness of the ribbon, which increases stuffing and ribbon movement problems.
Increased flow resistance and coefficient of friction from pigments result in increased back pressure on the ribbon, which leads to ribbon jams. Feeding typically is by opposed, intermeshed gears or pinch rollers, and high tensions can damage the ribbon both at the drive gears and at the printhead since the ribbon typically moves past the printhead. Similarly, the ribbon may slip at the drive gears, resulting in light, inconsistent printing and fabric damage which can lead to complete ribbon feed failure.
Pigments, such as carbon black, are well suited to printing bar code to be sensed conventionally using infrared radiation. It is generally known that particulate coloring matter such as pigments in conventional printer ribbons do not migrate, and that characteristic is a factor in this invention.
This invention employs re-inking on the print track only. The mechanism for such re-inking was invented prior to this invention, and is described in U.S. Pat. No. 5,015,108; a continuation of patent application Ser. No. 360,182, filed June 1, 1989, by J. H. Paterra, et al, and entitled "Ribbon Print Track Reinking with a Roll System." The presence of dye in the fabric seems to replenish the print track and extend ribbon life, and the ribbon is suitable for general purpose uses as well as for bar code applications.